The ABCs of species evolution

December 23, 2020

Almost four decades of research have led scientists at Japan's Institute for Integrated Cell-Material Sciences (iCeMS) to propose that a family of transporter proteins has played an important role in species evolution. One protein in particular, called ABCA1, was likely crucial for vertebrate evolution by helping regulate when signals involved in cell proliferation, differentiation and migration enter a cell. This process was necessary for vertebrates to develop into more complex organisms with sophisticated body structures.

The ATP-binding cassette proteins (ABC) are very similar across species, including in bacteria, plants and animals. There are different types of ABC proteins with different transportation roles, importing nutrients into cells, exporting toxic compounds outside them, and regulating lipid concentrations within cell membranes.

iCeMS cellular biochemist Kazumitsu Ueda has studied human ABC proteins for 35 years, ever since he and his colleagues identified the first eukaryote ABC protein gene.

"We believe ABC proteins must have played important roles in evolution," Ueda says. "By transporting lipids, they enabled plants and animals to thrive on land by protecting them from water loss and pathogen infection. They are also assumed to have accelerated vertebrate evolution by allowing cholesterol to function as an intra-membrane signalling molecule."

Organisms that existed early in Earth's history were probably formed of DNA and proteins surrounded by a leaky lipid membrane. As the organisms evolved, their membranes were fortified to protect them from the external environment. But this meant only organisms that evolved special ABC transporters capable of carrying nutrients across the membrane survived. The ABC proteins also played important roles in generating an outer membrane that protected cells from external stresses and in removing harmful substances from inside.

Recently, Ueda and his team studied the roles of ABCA1, gaining deeper insight into how it regulates cholesterol. Specifically, they found that ABCA1 exports cellular phospholipids and cholesterol outside the cell for generating high-density lipoproteins, popularly called good cholesterol.

They also found that ABCA1 constantly flops cholesterol from the cell membrane's inner leaflet to its outer leaflet, maintaining a lower concentration on the inner side. This flopping is temporarily suppressed when the cell is exposed to an external stimulus, like growth hormone. The resultant accumulation of cholesterol in the inner leaflet triggers the recruitment of proteins to the membrane and modulates the signal transduction. Ueda and his team suggest that ABCA1 allowed vertebrates to evolve complicated biological processes and sophisticated bodies.

"ABCA1 is very unique and its functions surprised us," says Ueda. "Cholesterol's role was thought to focus mainly on physically strengthening the cell membrane and reducing its permeability to ions. Our research suggests it played a more important role in vertebrates, accelerating their evolution."
-end-
DOI: 10.1002/1873-3468.13945

About Kyoto University's Institute for Integrated Cell-Material Sciences (iCeMS): At iCeMS, our mission is to explore the secrets of life by creating compounds to control cells, and further down the road to create life-inspired materials. https://www.icems.kyoto-u.ac.jp/

For more information, contact: I. Mindy Takamiya/Mari Toyama
pe@mail2.adm.kyoto-u.ac.jp

Kyoto University

Related Evolution Articles from Brightsurf:

Seeing evolution happening before your eyes
Researchers from the European Molecular Biology Laboratory in Heidelberg established an automated pipeline to create mutations in genomic enhancers that let them watch evolution unfold before their eyes.

A timeline on the evolution of reptiles
A statistical analysis of that vast database is helping scientists better understand the evolution of these cold-blooded vertebrates by contradicting a widely held theory that major transitions in evolution always happened in big, quick (geologically speaking) bursts, triggered by major environmental shifts.

Looking at evolution's genealogy from home
Evolution leaves its traces in particular in genomes. A team headed by Dr.

How boundaries become bridges in evolution
The mechanisms that make organisms locally fit and those responsible for change are distinct and occur sequentially in evolution.

Genome evolution goes digital
Dr. Alan Herbert from InsideOutBio describes ground-breaking research in a paper published online by Royal Society Open Science.

Paleontology: Experiments in evolution
A new find from Patagonia sheds light on the evolution of large predatory dinosaurs.

A window into evolution
The C4 cycle supercharges photosynthesis and evolved independently more than 62 times.

Is evolution predictable?
An international team of scientists working with Heliconius butterflies at the Smithsonian Tropical Research Institute (STRI) in Panama was faced with a mystery: how do pairs of unrelated butterflies from Peru to Costa Rica evolve nearly the same wing-color patterns over and over again?

Predicting evolution
A new method of 're-barcoding' DNA allows scientists to track rapid evolution in yeast.

Insect evolution: Insect evolution
Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich have shown that the incidence of midge and fly larvae in amber is far higher than previously thought.

Read More: Evolution News and Evolution Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.